This is touched in “PowerShell Execution Policies in Standard Images” on Lee Holmes’ Blog and “PowerShell’s Security Guiding Principles” on the Windows Power Shell Blog
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Summary
Some machines treat UNC paths as the big bad internet, so PowerShell treats them as remote files. You can either disable this feature on those servers (UncAsIntranet = 0,) or add the remote machines to your trusted hosts.
If you want to do neither, PowerShell v2 supports an -ExecutionPolicy parameter that does exactly what your pseudocode wants. PowerShell -ExecutionPolicy Bypass -File (...).