▁at ▁arms , ▁who ▁det ained ▁him ▁in ▁a ▁room ▁at ▁the ▁Will ard ▁Hotel . ▁ ▁While ▁it ▁has ▁been ▁said ▁that ▁" C ong ress ▁is ▁hand c uff ed ▁in ▁getting ▁obst inate ▁witness es ▁to ▁comp ly ", ▁cases ▁have ▁been ▁referred ▁to ▁the ▁United ▁States ▁Department ▁of ▁Justice . ▁The ▁Office ▁of ▁Leg al ▁Coun sel ▁has ▁assert ed ▁that ▁the ▁President ▁of ▁the ▁United ▁States ▁is ▁protected ▁from ▁cont empt ▁by ▁executive ▁privile ge . ▁ ▁Sub po enas ▁Cong r essional ▁rules ▁emp ower ▁all ▁its ▁standing ▁comm itte es ▁with ▁the ▁authority ▁to ▁comp el ▁witness es ▁to ▁produce ▁testim ony ▁and ▁documents ▁for ▁subjects ▁under ▁its ▁juris diction . ▁Committee ▁rules ▁may ▁provide ▁for ▁the ▁full ▁committee ▁to ▁issue ▁a ▁sub po ena , ▁or ▁permit ▁sub comm itte es ▁or ▁the ▁chairman ▁( act ing ▁alone ▁or ▁with ▁the ▁ranking ▁member ) ▁to ▁issue ▁sub po enas . ▁ ▁As ▁announced ▁in ▁Wil kin son ▁v . ▁United ▁States , ▁a ▁Cong r essional ▁committee ▁must ▁meet ▁three ▁requirements ▁for ▁its ▁sub po enas ▁to ▁be ▁" leg ally ▁sufficient ." ▁First , ▁the ▁committee ' s ▁investigation ▁of ▁the ▁broad ▁subject ▁area ▁must ▁be ▁author ized ▁by ▁its ▁chamber ; ▁second , ▁the ▁investigation ▁must ▁purs ue ▁" a ▁valid ▁legisl ative ▁purpose " ▁but ▁does ▁not ▁need ▁to ▁involve ▁legisl ation ▁and ▁does ▁not ▁need ▁to ▁specify ▁the ▁ult imate ▁intent ▁of ▁Congress ; ▁and ▁third , ▁the ▁specific ▁in qui