Use PutObjectLegalHold with an Amazon SDK or CLI

    /// <summary>
    /// Set or modify a legal hold on an object in an S3 bucket.
    /// </summary>
    /// <param name="bucketName">The bucket of the object.</param>
    /// <param name="objectKey">The key of the object.</param>
    /// <param name="holdStatus">The On or Off status for the legal hold.</param>
    /// <returns>True if successful.</returns>
    public async Task<bool> ModifyObjectLegalHold(string bucketName,
        string objectKey, ObjectLockLegalHoldStatus holdStatus)
    {
        try
        {
            var request = new PutObjectLegalHoldRequest()
            {
                BucketName = bucketName,
                Key = objectKey,
                LegalHold = new ObjectLockLegalHold()
                {
                    Status = holdStatus
                }
            };

            var response = await _amazonS3.PutObjectLegalHoldAsync(request);
            Console.WriteLine($"\tModified legal hold for {objectKey} in {bucketName}.");
            return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
        }
        catch (AmazonS3Exception ex)
        {
            Console.WriteLine($"\tError modifying legal hold: '{ex.Message}'");
            return false;
        }
    }

To apply a Legal Hold to an object

The following put-object-legal-hold example sets a Legal Hold on the object doc1.rtf.

aws s3api put-object-legal-hold \
    --bucket my-bucket-with-object-lock \
    --key doc1.rtf \
    --legal-hold Status=ON

This command produces no output.

    // Set or modify a legal hold on an object in an S3 bucket.
    public void modifyObjectLegalHold(String bucketName, String objectKey, boolean legalHoldOn) {
        ObjectLockLegalHold legalHold ;
        if (legalHoldOn) {
            legalHold = ObjectLockLegalHold.builder()
                .status(ObjectLockLegalHoldStatus.ON)
                .build();
        } else {
            legalHold = ObjectLockLegalHold.builder()
                .status(ObjectLockLegalHoldStatus.OFF)
                .build();
        }

        PutObjectLegalHoldRequest legalHoldRequest = PutObjectLegalHoldRequest.builder()
            .bucket(bucketName)
            .key(objectKey)
            .legalHold(legalHold)
            .build();

        getClient().putObjectLegalHold(legalHoldRequest) ;
        System.out.println("Modified legal hold for "+ objectKey +" in "+bucketName +".");
    }