Straighten me out here

Somebody said recently:

REAL law enforcement doesn't put such "tools" [trojans] on
people's machines. Not after firewalls, keylogger detectors and such. It'd
be a waste of time, resources and court orders that might tip off the
peson being investigated. Inserting a transmitter, or tapping the phone
line is a more commonplace method where required. In MANY cases though,
there's enough radio frequency energy coming right off the computer or the
monitor that all that's required is parking a van down the street and
sniffing the signals out of the computer. Assuming that a transmitter
hasn't been placed directly into the keyboard.

I thought that the bill passed a few years ago - not the Patriot act, some
other thing, allowed law enforcement to drag information from computers any
way they could.

If they have a list of possible 'terrorists', say 5000 people, even the
American government isn't capable of breaking into the homes of so many
'terrorist' suspects and planting transmitters on their computers; surely
they are using trojans, delivered, perhaps, through free software of good
quality, that a lot of people want to have. Or maybe through the OS, or
through a chip maker that has been co-opted, or combinations of the above,
or....you name it.

Can anybody comment on whether this assumption makes more sense than the
statement above, that law enforcement/TLAs prefer to physically plant a bug
in a computer? I'm not talking about some Mafia bigshot they are dying to
convict, but the mass surveillance of 'terrorists' they must be dying to
implement, if they haven't already done it.