"It could be a long period of time like several years, or maybe analysis would show another period of time that might be appropriate," Van Hollen said during a media call.
The senator had asked the SEC to look into stock performance after buyback announcements to determine the impact on individual stocks. What the study found, as reported in a letter from Commissioner Robert L. Jackson Jr., was that "firms that let insiders sell on buyback announcements perform worse over the long run," Van Hollen said.
"In other words, the executives' gain is at the expense of the other stock holders who are not insiders," he added. "It raises the concern that buybacks are used as a way to maximize executive pay."
The senator's comments come as share repurchases, announcements of which totaled more than $1 trillion in 2018, have come under bipartisan fire.
Earlier this year, Sens. Charles Schumer, a New York Democrat, and Bernie Sanders, a Vermont independent who is running for president on the Democratic ticket, unveiled a plan that would force companies engaging in repurchases to pay a living wage and provide health-care benefits.
Shortly after, Florida Republican Sen. Marco Rubio said he wanted to change tax laws that reward buybacks.