Come to a halt, back down. For example, During a recession, many businesses are forced to draw in the reins on expansion. This expression transfers the means of stopping a horse to other kinds of restraint.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.