There isn't anything particularly illegal about them, but in many places (sea shores) they are considered a weapon and cannot be used legally. I have seen some explicit references to them from some parks services. This is an excerpt from the NPS webpage for Padre Island:
Bait Launchers:
Question: Am I allowed to use a compressed gas powered bait launcher within Padre Island National Seashore?
Answer: According to 36 Code of Federal Regulations, such a device is considered a weapon. Federal regulations limit the use of weapons in the National Seashore. The use of a weapon within the Seashore is prohibited unless the time and location of its use is specifically designated. Pending such designation by the park Superintendent, the use of these devices is prohibited.
Question: Can an exception be made for someone with a disability which prevents their ability to cast?
Answer: The use of a weapon to aide in casting due to a disability is prohibited. People frequently surf fish at the National Seashore without distance casting;many use short rods and fish between the first and second sandbar and/or the second and third sandbar. There are also local options that negate the need to distance cast at Bob Hall Pier at Padre Balli Park, Packery Channel (North and South Jetties), and many places along the Laguna Madre.
So it really just depends and no you cant claim 'ADA'.