I cannot change the LockState of Private and shared channel sites, is there any official document about this behavior ?

Hello @Huynh Tran Trung Hieu,

Thank you for your question and for sharing the error message.

Based on the current design of Microsoft Teams and SharePoint Online, this behavior is expected and by design, rather than something caused by a missing configuration.

In Microsoft Teams, each team is connected to a Microsoft 365 group where membership is managed centrally. Files that you see in the Files tab of a team are stored in SharePoint. For standard channels, all channels share the same SharePoint site. However, for private and shared channels, Teams automatically creates a separate SharePoint site for each channel to ensure that access is strictly limited to the channel’s members.

Because these private and shared channel sites are tightly managed by Microsoft Teams, certain SharePoint administrative actions are intentionally restricted to avoid breaking the Teams experience or causing access inconsistencies. One of those restrictions is that private and shared channel sites cannot be locked or set to ReadOnly/NoAccess using the LockState property. This is why the PowerShell command returns the message that these sites are not allowed to be locked.

At the moment, there is no official Microsoft article that directly calls out the LockState limitation specifically for private or shared channel sites. However, you may find it helpful to review the following documentation, which explains how Teams‑connected SharePoint sites are structured and managed: Teams and SharePoint integration - SharePoint in Microsoft 365 | Microsoft Learn

This article provides useful background on how Teams and SharePoint work together and helps explain why some SharePoint site controls behave differently for Teams channel sites.

I hope this helps clarify the behavior. Please feel free to let me know if you have further questions

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Private and shared channel sites created by Microsoft Teams have special behavior when SharePoint Information Barriers are enabled. Their access is governed by the Information Barriers mode rather than by the standard SharePoint LockState setting.

For private channel sites specifically:

• When SharePoint Information Barriers are enabled, each new private channel site automatically inherits the parent team’s Information Barriers (IB) mode within 24 hours.
• The IB mode for a private channel site can be:
  • Open – normal site access and sharing per the site’s sharing policy.
  • Implicit – access is restricted only to current members of the private channel, and sharing is limited to “People with existing access” links.
• Existing private channel sites default to Open IB mode. To change them to Implicit, use:

    Set-SPOSite -Identity <site URL> -InformationBarriersMode Implicit
  

Because access control for these Teams-connected private channel sites is handled through Information Barriers mode, they are not intended to be managed via LockState (for example, ReadOnly or NoAccess) in the same way as regular SharePoint sites. The error shown when running Set-SPOSite -LockState on a private or shared channel site reflects this behavior.

To control access for these sites, configure the Information Barriers mode instead of trying to lock them with LockState.

References:

• Use Information Barriers with SharePoint
• Lock and unlock sites
• Set-SPOSite