State police were protecting the building and trying not to allow the protesters to gain access to the House floor, according to images and videos posted by activists on Twitter.
The Legislature at the time was debating whether to extend the governor's state of emergency.
A police spokesman told NBC News that it is legal in Michigan to bear arms, so long as the weapons are visible and all other laws are obeyed.
On 23 March, Whitmer issued a "Stay Home, Stay Safe" executive order, which prohibits local residents from leaving their homes for work unless designated as "critical infrastructure" workers and banned public gatherings and visits to local hospitals, malls or restaurants.
Whitmer then extended the executive order until the end of April. Although lockdowns, quarantines, and states of emergency were declared and repeatedly extended in dozens of countries and regions worldwide, even in those with far less COVID-19 victims than in the US, Michigan residents viewed the governor's order as being excessive.
President Donald Trump has been advocating for states to reopen their economies and made a call-to-action earlier in April after he said that the states of Minnesota, Michigan, and Virginia must be "liberated" from restrictions imposed by their Democratic governors. Medical experts for their part have been arguing that the economy should be reopened only after expanding testing capabilities across the country.