They have jurisdiction everywhere within the US, but enhanced powers near the borders. Some details in [0].
Specifically, they have the right to search and seize "with no suspicion of unlawful activity" within 100 miles of any border - including sea borders, so that's about 70% of the US by population. Also anywhere around international airports and inland waters "with ready access to the open sea", but the 100-mile zone doesn't appear to apply there.
Certain other powers are limited to 10 or 25 miles from the border.
Specifically, they have the right to search and seize "with no suspicion of unlawful activity" within 100 miles of any border - including sea borders, so that's about 70% of the US by population. Also anywhere around international airports and inland waters "with ready access to the open sea", but the 100-mile zone doesn't appear to apply there.
Certain other powers are limited to 10 or 25 miles from the border.
[0] https://crsreports.congress.gov/product/pdf/LSB/LSB10559