If you are talking Florida, Wels are neither conditional nor prohibited:
http://www.myfwc.com/wildlifehabitats/nonnatives/conditional-prohibited-species/conditional/
http://www.myfwc.com/wildlifehabitats/nonnatives/conditional-prohibited-species/prohibited/
http://www.myfwc.com/wildlifehabitats/nonnatives/conditional-prohibited-species/conditional/
http://www.myfwc.com/wildlifehabitats/nonnatives/conditional-prohibited-species/prohibited/