XSLT: Bypassing elements of a given namespace

identity-ns-bypass.xsl

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:ns1="http://s1">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match=
 "*[not(attribute::ns1:*)
  and
    not(descendant-or-self::ns1:*)
   ]
 |
  @*[not(namespace-uri()='http://s1')]
 "/>
</xsl:stylesheet>

input-sample.xml

<Collection xmlns="http://s0" xmlns:ns1="http://s1">
  <Identifier Name="CollectionX"
          ns1:GlobalID="{E436833B-B0A6-4E0D-804B-60052B767AE3}"
          ns1:LocalID="{0130C866-7A91-4544-A82B-E0C0F2E3BCB2}"  />

  <Properties>
    <ns1:Collectible>1982</ns1:Collectible>
    <Displayed>Reserved</Displayed>
    <Picture>Reserved.jpeg</Picture>
  </Properties>

  <WeakLinks>
    <Link Type="resource" Language="en-us"/>
  </WeakLinks>

</Collection>

result.xml

<?xml version="1.0" encoding="utf-8"?>
<Collection xmlns="http://s0" xmlns:ns1="http://s1">
  <Identifier 
      ns1:GlobalID="{E436833B-B0A6-4E0D-804B-60052B767AE3}"
      ns1:LocalID="{0130C866-7A91-4544-A82B-E0C0F2E3BCB2}"  />

  <Properties>
    <ns1:Collectible>1982</ns1:Collectible>
  </Properties>

</Collection>

This transform overrides the identity rule to filter all elements/attributes which do not belong to the target namespace and are not parent of elements/attributes with the target namespace.

Credits.