In your post, you stated:

However, the court inHellerclarified that while the Second Amendment offers the most significant safeguards when it comes to protecting one's right to own a firearm within their home, these protections have certain boundaries. Like other fundamental rights, the right to possess and own a gun is not absolute and may be subject to government rules (Kopel,2020). For instance, individuals who have been convicted of felonies and those with mental illnesses are not allowed to buy firearms. This opinion could have informed the state of Varneyland's decision to deny Tedd the chance to register his firearms because of his history with mental illness, suicidal and self-harm tendencies.

As you noted, the Heller case held that the 2nd Amendment isn't absolute. But remember that Heller addressed people who have been involuntarily institutionalized rather than those who are "mentally ill." Isn't the focus on whether the restrictions are reasonable? So, couldn't it be argued that it was unreasonable to bar a fellow for had a single mental health episode from owning guns?

District of Columbia v. Heller, 554 U.S. 570, 128 S. Ct. 2783, 171 L. Ed. 2d 637 (2008).

Hope v. State, 133 A.3d 519, 163 Conn. App. 36 (App. Ct. 2016).

Kopel,D.B. (2020). Red flag laws: Proceed with caution.SSRN Electronic Journal,45, 1-31.https://doi.org/10.2139/ssrn.3653555