Federal agencies are explicitly affirmative authority grants. Their powers are laid out in those acts.
They can only do those things.
They cannot do other things just because "no law restricts it".
The exact authority grant is complicated.
You want:
https://www.law.cornell.edu/uscode/text/15/78d
and following sections, plus a whole bunch of stuff enacted elsewhere.
The part you are probably most looking for is:
https://www.law.cornell.edu/uscode/text/15/78u
There you can see most clearly their civil authority and what they are allowed to do.
You can see it says "Whenever it shall appear to the Commission that any person is engaged ... in acts or practices constituting a violation of {a bunch of stuff} .. it may in its discretion bring an action ... to enjoin such acts or practices ... .
The Commission may transmit such evidence as may be available concerning such acts or practices as may constitute a violation of any provision of this chapter or the rules or regulations thereunder to the Attorney General, who may, in his discretion, institute the necessary criminal proceedings under this chapter"
It then goes on to add additional monetary penalty authority that you see exercised here.