The expulsion order was Halleck's fault

The Politico:
On this day in 1862, Gen. Ulysses S. Grant (1822-1885) issued an order during the Civil War expelling Jews from a large region occupied by the Union Army.
[...] Grant came under the influence of Henry Halleck, the Union armies’ general-in-chief, who directly linked “traitors” with “Jew peddlers.”
Or was it Grant's father's influence? Why can't this be Grant's decision?.