it violates the freedom of association by imposing warrantless surveillance.
I am pretty strong strict constructionist who is also willing to read in some implicit rights where I feel they are necessary to exercise the other explicit rights. The 9th amendment exists to support that interpretive action.
For examples, if I were a SCOTUS justice I would hold that the various travel restrictions like the no-fly list are unconstitutional because there is no due process around who is on the list. We have an explicit right to association and assembly in the first amendment. One must be able to go to where the assembly is taking place, if air travel is the only reasonably way to get there due to say time constraints, the government cannot prevent a citizen from traveling by air, without due process of law.
I find your argument that surveillance violates the freedom of association however. They government clearly is denied the power to prevent you from associating, but I don't see any explicit right to associated in secret. An association is not an effect, and while it might involve your person being present or not, it does not require the violation of your person to observe it. So I am struggling to find an implied privacy right here using the fourth amendment.
I am not sure there is a constitutional issue here. I do think there is a violation of law taking place however. Essentially you have a contract with the cellular carrier to interface your equipment with their own. These devices misrepresent the LEA as the carrier to your device. I don't see how this is any less fraudulent than if an officer arrived at your home dressed as gas company employee and professing to be from the gas company investigating an issue, and subsequently made the argument that you could be prosecuted for the contraband discovered in your home based on the fact that he was invited in and therefore did not require a warrant.
Plain clothes cops are one thing but to me these devices cross a line in that they are actively misrepresenting what/who they are. This possibly induces you to do things that might be materially against your interest like self incrimination. This is a form for fraud.