new york president donald trump announcement wednesday ban transgender people serve u.s. military unleash storm legal threats advocate say seek plaintiffs want file suit trump surprise tweet make clear ban reverse former president barack obama policy would go effect whether apply serve members military wish join u.s. defense department actively root transgender people discharge military pentagon likely face especially contentious fight legal experts say valid justification exclude transgender people military say jon davidson legal director lgbt right group lambda legal currently serve without problem extraordinary cost disruption experts say single transgender people would violate right equal protection law guarantee u.s. constitution joshua block american civil liberties union say inbox flood email trump ban include service members think important thing people understand immediate future nothing happen ... trump tweet self-executing say block senior staff attorney lesbian gay bisexual transgender lgbt issue obama defense department declare june 20016 transgender people could serve openly arm force pentagon consider second step allow openly transgender people enlist trump wednesday issue three tweet say transgender people would allow serve capacity military cite disruptions medical cost pentagon refer question white house press secretary sarah huckabee sanders say trump make decision consultation national security team defense department would work white house take lead lawful implementation sarah warbelow human right campaign legal director say trump declaration amount discrimination basis sex identity therefore open legal challenge court provide quite bite deference military determine policies say however mean military law pentagon may clear path ban merely prevent new transgender recruit sign ban apply seek enlist legal bar would high military already wide leeway exclude class people base medical need block say trump want remove exist transgender servicemembers rank unclear legal mechanism could use forcibly discharge u.s. troop transgender people disclose identity result obama policy policy change would legal recourse arbitrarily deny job benefit davidson say even seek enlist might allege government ban transgender individuals arbitrary way without good reason least one legal expert say challenge would difficult mount court typically defer government military matter eugene fidell teach military law yale law school say even discharge transgender service members ask military review case decisions could overturn secretaries four branch military political appointees would difficult convince federal court reverse secretaries fidell say u.s. military transgender ban could face major legal challenge