The arguments against ISAP are legion
Alternatives to detention are not even plausible subjects for experiment unless the criminal penalties for failing to appear are employed.
Only when ordinary absconders – who aren't sexual predators or terrorists but just illegal aliens who ignore their court dates – are routinely given stiff prison sentences can alternatives to detention even be plausibly considered.
The pervasive unwillingness of illegal aliens to comply with immigration law in the absence of detention is not surprising.
Unlike in the criminal justice setting, where failing to appear often results in additional penalties, a final order of removal is all an illegal alien realistically faces, whether he shows up to immigration court or not.
Though the law provides for imprisonment of up to 10 years for aliens who fail to appear at their hearings, the chances that an immigration absconder not involved in additional crimes will be prosecuted are vanishingly small.
Furthermore, those failing to appear for immigration proceedings are likely to avoid detection for many years, perhaps for the rest of their lives, given authorities' still-frivolous approach to tracking down immigration absconders.
For example, under pressure from advocacy groups, many police departments refuse to serve ICE administrative warrants issued to absconders, thus shielding the scofflaws from facing the consequences of failing to depart.
Thus, alternatives to detention are simply irrelevant for those likely to be rejected for asylum or cancellation of removal – i.e. the majority of those in removal proceedings.
In other words, "alternatives to detention" is simply a synonym for "catch and release."
https://cis.org/Moving-Toward-More-Effective-Immigration-Detention-Management