A reader emailed in the following comment about Michigan's wiretapping law:

I do believe that your definition on Michigan wiretapping is inaccurate. I
have reviewed the laws on the Michigan Legislature website and here is
what is stated.
750.539c Eavesdropping upon private conversation.

Sec. 539c.

Any person who is present or who is not present during a private
conversation and who wilfully uses any device to eavesdrop upon the
conversation without the consent of all parties thereto, or who knowingly
aids, employs or procures another person to do the same in violation of
this section, is guilty of a felony punishable by imprisonment in a state
prison for not more than 2 years or by a fine of not more than $2,000.00,
or both

Then if you read the definition of eavesdropping

750.539a Definitions.

Sec. 539a.

As used in sections 539a to 539i:

(1) “Private place” means a place where one may reasonably expect to
be safe from casual or hostile intrusion or surveillance but does not
include a place to which the public or substantial group of the public has
access.

(2) “Eavesdrop” or “eavesdropping” means to overhear, record,
amplify or transmit any part of the private discourse of others without
the permission of all persons engaged in the discourse. Neither this
definition or any other provision of this act shall modify or affect any
law or regulation concerning interception, divulgence or recording of
messages transmitted by communications common carriers.

(3) “Surveillance” means to secretly observe the activities of another
person for the purpose of spying upon and invading the privacy of the
person observed.

(4) “Person” means any individual, partnership, corporation or
association.

It isn't cut and dry but it does say "without the permission of all
persons engaged in the discourse." It is my understanding that
Eavesdropping is not just referring to others outside of the conversation.
It looks as if Michigan is an All-consent law state.

Not to mention, any other referrence is referring to Michigan as in the
very least a 2 party consent state. If you have any information on why
Michigan is a one-party consent, I would love to see it for my benefit. I
don't believe the law is defined clearly in your website.

We did a bit of research, modified the Michigan legal guide page, and provided the following response:

You are right that the language of the statute makes Michigan look like a two-party consent state.  However, the Sullivan v. Gray case cited on the legal guide page still appears to be good law, and that case says that a participant to a conversation may record it without obtaining the consent of all the parties to the conversation (essentially 1-party consent).  That said, given that Sullivan v. Gray is a mid-level appellate decision and the Michigan Supreme Court has not ruled on the question, I thought it advisable to soften the language on the page and to reflect the uncertainty that surrounds the issue.

Our reader helpfully turned our attention to an article from the Michigan Family Law Journal that discusses the Sullivan v. Gray case and concurs that participants in a conversation may record it without the consent of the other parties.  The relevant discussion begins on page 9.