Legal scholars say it is unclear how such a step would play out, but they agree a court test would likely focus on whether an emergency actually exists on the southern border and on the limits of presidential power over taxpayer funds. Trump is unhappy with a bipartisan border security bill that is going through Congress to avert another government shutdown, because it contains only a fraction of the funds he demanded for his promised border wall. The White House said Trump would sign the bill but declare a national emergency to try to obtain funds for the wall.