Where in the US has number 1 been done? I am not aware of any places where the offender is required to alert people. Most commonly they need only to report to the local government/police who then may (and may be required) to publish that info.
Often that is also often a condition of probation, meaning they are still under the authority of the courts and are still being "punished" by the system in leiu of prison. This is seen as the individual "giving up" some of their rights either by committing the offense or agreeing to the terms of probation instead of prison. This would also apply to #2.
Neither one of those justification for infringement of the 1st amendment would apply in the cases of an NSL which are already on very very shaky legal ground and gag orders on them have been ruled constitutional in the past, currently they are only constitutional because a person getting an NSL now as the ability to appeal the NSL to a federal court, something that was previously missing
Forcing factual speech (such as disclosures, warnings, product information, truth-in-lending, etc) is a lot different than forcing someone to say something that isn't true.
The better example here is warning labels. Presumably, part of the reasons warning labels are easily compelled by the government is that they involve commercial speech, which receives a lower degree of 1A scrutiny. But then, most warrant canaries fall into the same bucket; they're basically just an inverted warning label.
For people who have become involved with national security issues, aren't they often required to deny being involved with national security issues if asked? Would that count?
No I don't think it does. The paperwork they sign when they get their security clearances put those people in a special circumstance. American journalists, not having security clearances, are allowed to spill the beans on national secrets.
Often that is also often a condition of probation, meaning they are still under the authority of the courts and are still being "punished" by the system in leiu of prison. This is seen as the individual "giving up" some of their rights either by committing the offense or agreeing to the terms of probation instead of prison. This would also apply to #2.
Neither one of those justification for infringement of the 1st amendment would apply in the cases of an NSL which are already on very very shaky legal ground and gag orders on them have been ruled constitutional in the past, currently they are only constitutional because a person getting an NSL now as the ability to appeal the NSL to a federal court, something that was previously missing