There are two types of announcements.
One is Merit Promotion, which you can allow status candidates to apply. They get no special placement because of Veterans Preference, but they do get to compete with Government Employees (Schedule A also falls into this category). Now, if an Agency announces a position to people in the Government, but outside their Agency, they must allow Veterans to apply (part of VEOA). The intent was for Veterans to have opportunities that they would not normally have to apply for government jobs. Some Agencies will issue one list, others will issue two, with the Veterans on a list of their own. The key to a Merit Promotion announcement is the Vets get to apply, even though they may not get preference. Or, if you look at it this way, by having Veterans Preference, they get to apply.
Then you have what is commonly called a DEU Announcement to all US Citizens. On this list, Veterans Preference does apply. On these qualified 10% or more qualified disabled Veterans go to the top of the list, end of statement. To bypass a 30% disabled Vet requires an exception to policy from OPM. To bypass a 10-20% disabled Vet requires approval at the Agency Secretary level (who use the same criteria as OPM, so in reality there isn't much difference). So on a DEU list first we have all the qualified disabled Vets at the top. Now the rest of the list can be set up one of 3 ways. If it is an unranked list, qualified 10% or more Disabled Vets are on the top, the next is the 10 point Vets, followed by the 5 point Vets, then everyone else. If you are using the rule of 3, still on the books, but not used that much anymore, the 10 point Vets and the 5 point Vets have the points added to their score, but you can't bypass a disabled Veteran without going through the bypass process. Then you have category ranking and rating. 10% or more disabled vets still go to the top of the top category (most training will just gloss over this part), and all other applicants broke down by the raw score, placed in the categories (usually 3, but doesn't have to be, but must be at least 2). Then the points are added. Non-disabled Veterans don't go to the top of their category, but you can't hire a non-Vet from the top Category when Vets area available(most training will gloss over this also ). So now, in the top category, will be at the top qualified 10% or more disabled Vets, followed by the everyone else in score order. But, if there are any Vets in the top category, you can't hire a Non-Vet as long as there are Vets available in that category. What a lot of managers don't realize is that a if a disabled Vet meets minimum qualifications, then they are qualified, end of statement, and go to the top of the list. One commenter stated that this is only after interviews and Subject Matter Expert Reviews, etc.. 5 USC and 5 CFR are very specific that Veteran preference is applied before the certification is prepared, not after it. We are not talking about best qualified, for the disabled Vets, we are talking qualified, and qualified is qualified. And qualified is based upon the approved qualification standards, not some idea the manager may have about qualifications. This is a glass ball that you don't want to break. As I stated, where I work, back in 2005, they got hammered by OPM for violating Veterans preference , many got 2 week suspensions, 3 resigned under 75 actions, 2 were referred to OSC for prosecution, and they lost all staffing capability for 18 months, while what was left was retrained. The OPM view is that a qualified applicant can do the job, end of statement. And, the disabled Veterans wouldn't be on the list if they didn't meet minimum qualifications to start with. The catch to qualified is experience, such as 1 year at the next lower grade. There are substitutions where education can be used to substitute for experience. In this DEU situation, they will not allow management to send in a team of subject matter experts to tell them who meets minimum qualifications. They used to do that for the IT jobs, but enough HR Specialist have experience now in IT, that really isn't needed anymore. The analogy to letting management determine who is meets qualification standards before the certificate is issued is like putting the fox in charge of the hen house. Likewise, someone said a non-Vet could contest a decision just as easy as a Vet. Well, that isn't exactly accurate. A Veteran has numerous appeals process (with an open court room being only one). They can appeal through the Department of Labor, they can Appeal directly to the MSPB, or they can go the court route. The only way a non-Vet can appeal is to jump directly to court and they have to show that EEO rights were violated (which is difficult at best since the HR Specialist has no idea about race, religion, etc.). Also of note, numerous Veterans Organization are now providing free legal representation in situations where Veterans preference has been violated. This is a new phenomenon. I believe David mentioned a bunch of actions that are pending, many of which could set HR upside depending upon the decision.