Private/Test/Test-IsEA.ps1

function Test-IsEA {
    <#
        .SYNOPSIS
        Tests if the current user is a member of Enterprise Admins.
 
        .DESCRIPTION
        Checks if the current user is a member of the Enterprise Admins group by
        examining the user's security token for the well-known RID 519.
         
        Enterprise Admins is a forest-wide privileged group that exists in the
        forest root domain and grants administrative rights across all domains
        in the forest.
         
        This function uses SID-based checks against the user's token, requiring
        no network calls or AD queries, making it fast and reliable even when
        domain controllers are unreachable.
 
        .INPUTS
        None. This function does not accept pipeline input.
 
        .OUTPUTS
        System.Boolean
        Returns $true if the current user is a member of Enterprise Admins.
        Returns $false otherwise.
 
        .EXAMPLE
        Test-IsEA
        Returns $true if the current user is a member of Enterprise Admins.
 
        .EXAMPLE
        if (Test-IsEA) {
            Write-Host "User has Enterprise Admin privileges"
        } else {
            Write-Host "User does not have Enterprise Admin privileges"
        }
        Conditionally executes code based on Enterprise Admins membership.
 
        .NOTES
        Well-known RID checked:
        - 519: Enterprise Admins (forest-wide administrative group)
         
        This function checks the current user's security token, so it works offline
        and does not require Active Directory queries. It includes nested group
        memberships as they are expanded in the user's token at logon.
         
        Enterprise Admins only exists in multi-domain forests. In single-domain
        forests, Domain Admins effectively serve the same role.
 
        .LINK
        https://learn.microsoft.com/en-us/windows/win32/secauthz/well-known-sids
         
        .LINK
        https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/plan/security-best-practices/appendix-b--privileged-accounts-and-groups-in-active-directory
    #>

    [CmdletBinding()]
    [OutputType([bool])]
    param (
    )

    #requires -Version 5.1

    try {
        $identity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
        Write-Verbose "Checking if user '$($identity.Name)' has Enterprise Admin privileges"
        
        $enterpriseAdmins = $identity.Groups | Where-Object { $_.Value -match '-519$' }
        if ($enterpriseAdmins) {
            Write-Verbose "User is member of Enterprise Admins (RID 519)"
            return $true
        }
        
        Write-Verbose "User does not have Enterprise Admin privileges"
        return $false
        
    } catch {
        $errorRecord = [System.Management.Automation.ErrorRecord]::new(
            $_.Exception,
            'EnterpriseAdminCheckFailed',
            [System.Management.Automation.ErrorCategory]::NotSpecified,
            $identity
        )
        $PSCmdlet.WriteError($errorRecord)
        return $false
    }
}