And just when did he do this?
On April 27, 1861, about a week after the Fort Sumter surrender, President Lincoln ordered Winfield Scott, then head of the nation's military, to arrest anyone between Washington and Philadelphia suspected of subversive acts or speech, and his order specifically authorized suspension of the writ of habeas corpus. Scott passed the order down the line, and Southern sympathizers in Maryland were rounded up in batches.
Now, look the rest of this up and read about it like I did. Thanks.