Prohibiting the CIA/Pentagon from arming ISIS and 'al-CIA-duh' and the al-Nusra Front is an important step:
(i) It recognizes the REALITY of USA government funding of Islamic terrorists by Capital Hill.....its realistic.
(ii) Reduces the state funding of terrorism, since all modern terrorism is state funded, and it thus reduces the problem, at least in Syria. An army of 100,000 fighters can't survive without state support from some where.
On the other hand, as with Pakistan what happens when the legally proscribed organisation merely changes their name to avoid any court action? In Pakistan, terrorism is state sponsored:
They are the proxy army of the Pakistan armed forces who are run by the ISI, which in turn is funded and run by the CIA/Pentagon with 500,000 trained up recruits since 1979. This all started with Brzezinski initially, who as a British agent of influence of the Rothschilds borrowed the concept from Bernard Lewis a British Jewish super-spy intellectual embedded in Princeton University by the British state in the early 1970's, under the meme 'Arch of Crisis'..."Clash of Civilisation" "Destruction through destabilisation of the Soviet Union"....."The Bear trap"....etc:
Terrorist and Extremist Groups of Pakistan