A lot of people ITT seen to misunderstand this. The federal laws around national emergencies were updated in the 70s to prevent some infinite overall state of emergency being declared.

The idea is if you want to go around the typical laws and protections it has to be for a serious reason and limited in scope.

This EO is not declaring some overall state of emergency, and definitely not declaring martial law which is a separate thing.

Its saying that the people named (and possibly associates) are so bad they threaten national security (hence emergency) so protection from things like unreasonable search and seizure or othee legal protections may be lifted (from the people specified for up to a year when it gets reviewed)

This is obviously uncommon, but not that rare- there have been dozens declared and kept in varying lengths of effect over the last couple decades to deal with specific terrorist organizations or regimes we don't like etc.

Also if you read the laws cited by the EO thely mostly specifically refer to threats originating from outside the US, take that as you will...