If memory serves me right, this entire thing goes back to a court ruling that a warrant was needed, even on totally foreign communications via telephone because the way networks are constructed, those calls can end up going through a switch/router within the US even if both parties are outside of the US. The court somehow found that since a switch or router involved in the call may be in the US, it becomes a domestic issue.
Thats total nonsense.
The government has the ability to make people's lives miserable for pretty much any reason it wants. This power can be, and often is, abused to make people do things the government wants but has no legitimate authority to demand. There are limits to this power, though, since people will often balk at doing illegal things whose penalty would exceed the pain the government could assert for refusal.
Granting the government the power to protect people who do illegal actions on its behalf is very dangerous. To be sure, crooks already have too much power within the government, but to allow the government to extend its corrupting tentacles beyond itself is extremely dangerous.
Telecommunications wiretaps are just the beginning.